Sequential colour visual telepresence system

ABSTRACT

For implementing an anthropomorphic visual telepresence system with high resolution and low loop latency a sequential color video loop is provided. A sequential color camera sequentially captures color images, each captured image consisting of a portion of a single color component, and provides information as separate color information relating to portions of the sequentially sensed color images. The information is transmitted as separate color information. A sequential color display receives the transmitted information and displays sequentially each color image within the received information. Synchronization means synchronize the sequence and color of corresponding portions of images comprising a single color in said display with the portions of the images sensed by said camera.

This application is a continuation of U.S. patent application Ser. No.09/383,070 filed Aug. 26, 1999 now abandoned.

FIELD OF THE INVENTION

The present invention relates to visual telepresence systems. Moreparticularly, the present invention relates to an anthropomorphic visualtelepresence system having a high resolution and a low loop latency.

BACKGROUND OF THE INVENTION

The concept of telepresence has been in the public domain since theearly 1960s, when Ivan Sutherland demonstrated its basic principles. Twomajor components of a visual telepresence system are a head mounteddisplay (HMD) and its associated high speed servomechanism on whichvideo cameras are mounted. Two other important components of a visualtelepresence system are a head tracker and a communications systemlinking the HMD with the high-speed servomechanism. When an operator,wearing the HMD, moves her head in any direction, the head trackersenses that movement, sends the appropriate position data to thehigh-speed servomechanism, which thereby tracks in real-time or in nearreal-time the operator's head movements. Images from the video camerasmounted on the high-speed servomechanism are transmitted through thecommunications system to a display positioned in front of the eyes ofthe operator; for example, such a display forms part of the HMD. As aresult, the operator is given a visual impression similar to that from asame location as the remote cameras.

In order to describe this concept more accurately, the termanthropomorphic is often used, whereby a human-shaped configuration isimplied. Many systems have been referred to as telepresence systems, forexample a camera mounted on a pan and tilt servomechanism controlled bya joystick and in communication with a conventional monitor. Thisnecessitates the use of the term anthropomorphic to provide a moreaccurate description of human-shaped telepresence wherein the camera istracking in real-time or near real-time the head and/or eye movement ofan operator, and the images thereby gathered by the camera are displayeddirectly in front of the eyes of the operator.

The use of anthropomorphic visual telepresence is highly advantageousfor the operation of remote controlled vehicles. With currentadvancements in robotic technology the use of remote systems is steadilyincreasing, especially for performing tasks in hazardous environmentswhere the lives of people are at risk. Hazardous environments are found,for example, in nuclear installations where radiation is a significantconcern; in the production and handling of chemicals and explosives; inmining; and in underwater operations such as offshore oil exploration.Further applications include emergency, search and rescue operations, aswell as space applications, such as controlling robots and/or vehicleslocated in the environment of space, while remaining in the saferlocation of a spacecraft or other human-tended spaceborne habitat. Theoperator of the remote controlled vehicle is located in a safe place,from which he or she controls the vehicle using other human-machineinterface components such as a joystick, while the HMD gives him or herthe visual impression of being physically located at a same location asthe cameras, which are controlled by the movement of his or her head.

Generally, a telepresence system attempts to recreate an environment foran operator of a remote system. The better the environmental factors arerecreated, the more natural the resulting control process is. Of course,because the environmental factors are recreated, the “simulation” isoften implemented with safety in mind. For example, radiation levels arenot usually simulated other than by showing gauges of sensors within theremote system. In some instances, some environmental factors are alteredfor providing useful feedback. For example, temperature is raised andlowered to indicate temperature changes, but the simulated temperaturesare scaled for operator comfort and safety.

The human visual system is marvelous. From birth, our brain learns toprocess visual data. The visual data is real-time visual data (for themost part). To clarify, what is seen in a person's hand is felt in theirhand at the same time and in the same place. The latency between seeing,feeling and manipulating is truly negligible. This is particularly trueof the often occurring situation where a person rotates their headand/or eyes to center an object of interest into the so-called fovealarea of the human visual system, from the peripheral area where it waspreviously located. In such a situation, the brain almost instantlyprocesses new retinal information, and the object of interest isperceived without noticeable delay. Unfortunately, with anthropomorphicvisual telepresence systems, this is not so. A small latency of morethan a few tens of milliseconds is very noticeable. The brain of anoperator of an anthropomorphic visual telepresence system having such alatency is not used to dealing with such a delay. Hence,psycho-physiological discomfort results. Of course, when the latency isnegligible these reactions do not occur or are greatly lessened sincethe brain is operating in its normal mode of operation. It is also clearto those skilled in the art of visual telepresence that latency or timedelay between a movement of the HMD worn by the operator, and return ofcorresponding video images reflecting appropriate movement of thehigh-speed servomechanism, is a very critical parameter, and that thedegree of susceptibility to such latency varies among subjects.

Of course, a similar problem exists with image resolution. The human eyecaptures images at a high resolution. This resolution is actuallyvariable across the retina, from its maximum in the so-called fovealregion to its minimum in the peripheral region. For stationary images,the human brain assembles these images and enhances resolution oraccepts the limited resolution presented; however, for moving images,the quantisation—dividing the image into individual points—at a lowresolution results in choppy or discretised movement, as opposed tobeing relatively smooth and continuous as provided by the human visualsystem. For example, if each square inch of an image is displayed as asingle dot, from a location close to the display, a baseball wouldappear less round and its motion would appear to jump an inch at a time.This also results in psycho-physiological discomfort, such as headachesand nausea, when experienced continuously for extended periods of time.Therefore, it is clear to those skilled in the art of visualtelepresence that the resolution of displayed images is of primaryimportance. It is also well known to those skilled in the art of visualtelepresence that video image transmission using analog radio frequencytechniques is significantly less robust than video image transmissionusing digital radio frequency techniques. When using analog video imagetransmission, frequent interference-induced loss of horizontal and/orvertical synchronization signals may occur. This is significantlyreduced when using digitised video image transmission. Loss ofsynchronization also contributes to psycho-physiological discomfort ofan operator wearing the HMD. Therefore, it is often desirable to usedigitised video transmission. Unfortunately, this results in asignificant increase of the required radio frequency bandwidth fortransmission of the video signal. Digital signal compression anddecompression, also referred to as CODEC, reduces the required bandwidthbut results in added loop latency due to the image processing performed.In situations requiring the use of digitised video image transmission,an anthropomorphic visual telepresence architecture either uses a hightransmission bandwidth or suffers the added latency resulting from usingthe CODEC.

With regards to resolution for applications where colour is required,the implementation of field sequential colour imaging is verysuccessful. In field sequential colour imaging, a colour image iscomposed of a succession of primary colour components—typically red,green and blue—of the desired image. Several patents have been issuedfor sequential colour cameras. Similarly, many patents have been issuedfor sequential colour displays. The field of sequential colour displaysis generally a more recent field than that of sequential colour cameras.

It is well known to those skilled in the art of colour image displaysthat sequential colour displays, when using a sufficiently fastsequential rate so that the human brain will imperceptibly fuse theprimary colour images into full colour images, achieve a much highereffective resolution than the more conventionally used compositedisplays, for which it is implied that the information of all colours isdisplayed simultaneously instead of sequentially. This is due to thefact that in composite colour displays, a technique must be used inwhich the available display surface must be subdivided into severalprimary color groups often referred to as red green blue triads, thusleading to a resolution loss. With sequential colour displays, all ofthe display's resolution is available for each primary color, as thedisplay's surface does not have to be allocated among the three primarycolors.

U.S. Pat. No. 5,684,498 issued Nov. 4, 1997 to Welch et al. describesthe use of standard composite colour cameras in conjunction with asequential colour display forming part of a HMD. This approach leads tocolour fringing whenever the HMD is in motion at an appreciable rate.The method described by Welch suppresses colour fringing based on datafrom rate sensors measuring the motion of the HMD. This method suffersfrom the inherent inaccuracies of the rate sensors in detection of anacceleration of a head on which the HMD is mounted. Therefore, the imageshifting implemented to suppress colour fringing imperfectly correctsfor the colour fringing. The method taught by Welch does not achieve amaximum resolution because it uses a composite colour source at itsinput. Furthermore, the conversion of the composite colour signal into afield sequential colour signal results in additional loop latency.

It is, therefore, an object of this invention to provide ananthropomorphic visual telepresence system having a high resolution anda low loop latency.

It is further an object of this invention to provide an anthropomorphicvisual telepresence system enabling, when desired, the use of digitalvideo compression and decompression techniques, while maintaining looplatency within acceptable limits.

SUMMARY OF THE INVENTION

In accordance with the invention there is provided a sequential colouranthropomorphic visual telepresence system comprising:

-   a sequential colour camera for sequentially capturing colour images,    each captured image consisting of a portion of a single colour    component, and for providing information as separate colour    information relating to portions of the sequentially sensed colour    images;-   transmission means for transmitting an electrical signal including    the information as separate colour information;-   a sequential colour display for receiving the transmitted signal and    for displaying sequentially each colour image within the received    information; and,-   synchronization means for synchronizing the sequence and colour of    corresponding portions of images comprising a single colour in said    display with the portions of the images sensed by said camera.

BRIEF DESCRIPTION OF THE DRAWINGS

The preferred embodiments of this invention will now be described inconjunction with the attached drawings, in which:

FIG. 1 illustrates a visual telepresence system;

FIG. 2 illustrates a composite colour video loop according to the priorart;

FIG. 3 illustrates a colour video loop according to the prior artcomprising a composite colour camera and a sequential colour display;

FIG. 4 illustrates a field sequential colour video loop according to theinvention;

FIG. 5 illustrates a frame sequential colour video loop according to theinvention;

FIG. 6 illustrates a field sequential colour video loop with digitalimage compression and decompression according to the invention;

FIG. 7 illustrates a frame sequential colour video loop with digitalimage compression and decompression according to the invention;

FIG. 8 illustrates a sequential colour video loop with timing meansaccording to the invention.

In the figures “sc” refers to sequential colour, “t” refers to timeduration, “msec” refers to milliseconds, “f” refers to frequency, “Hz”refers to Hertz (cycles per second), and NTSC, PAL, and SECAM refer tocommonly known television signal standards. Using interlacing a fullimage, referred to as a “frame”, is composed of a successivepresentation of two half images, referred to as a “field”. Each “field”commonly consists of odd or even numbered image lines of a “frame”,respectively.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a basic visual telepresence system 100, with threeaxes of rotation used to emulate human neck movement. Two majorcomponents of the visual telepresence system 100 are a head mounteddisplay (HMD) 102, and its associated high speed servomechanism 104 onwhich video cameras 106 are mounted. Other important components of thevisual telepresence system 100 are a head tracker 108 and acommunication system 110 that links the HMD 108 with the high speedservomechanism 104. When an operator, wearing the HMD 102 moves her headin any direction, the head tracker 108 senses that movement and sendsappropriate position data to the high speed servomechanism 104, whichthereby tracks in real-time or in near real-time the operator's headmovements. Images from the video cameras 106 mounted on the high-speedservomechanism 104 are transmitted through the communications system 110to a display 112 positioned in front of the eyes of the operator; forexample, such a display forms part of the HMD 102. In some applicationstwo video cameras 106 are provided at a same distance as the human eyes.Images gathered by the two video cameras are simultaneously displayed infront of each of the operator's eyes, respectively, creating astereo-visional impression of three dimensional space imaged by thecameras.

Prior art visual telepresence systems, as shown in FIG. 2, use acomposite colour video loop 200. A composite colour camera 202 is linkedby a communication link 203 to a composite colour display 204. Incomposite colour video, all primary colours of a colour image aregathered simultaneously. Timing diagram 206 shows the timing ofinterlaced image fields comprising the odd and even numbered lines of animage separately sensed, transmitted and displayed. Table 208 shows thetiming and frequencies for commonly available prior art video systems.In composite colour video a severe reduction in resolution occurs, dueto the general arrangement of imaging sensors within, for example, asensor array in red, green and blue triads. Using this method, thereduction in resolution for a coloured image can potentially attain afactor of three along one axis, in comparison to the resolution offeredby a black and white or gray scale image for which the sensor'savailable pixels have not been shared among primary colour triads. Thisproblem is further exacerbated with many of the display technologiesoften used in HMDs, due to the relatively low fill factor, or percentageof the surface serving in the display of an image, attainable with suchtechnologies, along with the same triad arrangement situation previouslydescribed for composite colour cameras, which also adversely affects theresolution of such composite colour displays.

With regards to resolution for applications where colour is required,the implementation of sequential colour imaging is very successful. Infield sequential colour imaging, a colour image is composed of asuccession of primary colour components—red, green and blue—of thedesired image. Using a display based on this same sequential colourtechnique the human retina and brain naturally integrate these colourcomponents, if the rate at which the primary colour components arepresented is sufficiently high, and a single colour image is perceived.The actual frequency of sequential colour imaging at which the retinaand brain naturally integrate the colour components depends on theindividual, brightness of the image and interlacing. When required,sensors sensitive to wavelengths outside the visible spectrum, forexample infrared, are used. The sensed images are then converted intoimages comprising the primary colours of the visible spectrum fordisplaying.

FIG. 3 shows a visual telepresence system 300 according to Welch. Acomposite colour camera 302 is linked by a communication link 304 tocolour separation means 306 in the form of a colour separator. Theseparated colour images consisting of three primary colour images arethen converted into sequential colour images using parallel to serialconversion means 308 in the form of a parallel to serial converter whichis linked by a communication link 310 to a sequential colour display312. Timing diagram 320 shows the timing of interlaced image fields 322produced by the composite colour camera 302 and the timing of thesequential colour image fields 324 after the conversion. The timingdiagram 320 indicates the latency 326 resulting from colour separationand parallel to serial conversion. Table 330 shows the timing,frequencies and latency for commonly available prior art video systems.As is evident to those of skill in the art, the first primary colourimage displayed has a minimum latency of 0 seconds. The second primarycolour image has a minimum latency of ⅓ of the interval betweencomposite images; for NTSC, this is 1/180^(th) of a second. The thirdprimary colour image has a minimum latency of ⅔ of the interval betweencomposite images; for NTSC, this is 2/180^(th) of a second.

It is an object of this invention to provide an anthropomorphic visualtelepresence system having a high resolution and a low loop latency. Toachieve a maximum resolution in a visual telepresence system, it isnecessary to use a sequential colour camera as well as a sequentialcolour display. Specific means for synchronization (and sequencealignment) between camera and display is implemented in order tominimize loop latency. The anthropomorphic visual telepresence systemaccording to this invention is highly advantageous in applications wheresignificant concentration of an operator on a remote controlled vehicleis required. It eliminates or significantly reduces the main sources ofan operator's psycho-physiological discomfort and allows the use of sucha system for longer time periods or the use of such a system forcritical operations.

FIG. 4 shows an anthropomorphic visual telepresence system 400 accordingto the invention. A field sequential colour camera 402 is linked by acommunication link 403 to a field sequential display 404. The fieldsequential colour camera 402 operates on the same basic principles asfield sequential colour cameras described in prior art, excepting thatan output therefrom is a field sequential colour signal. Thecommunication link 403 is often a cable—for example, in environmentssuch as nuclear facilities—but is sometimes a wireless communicationslink—for example, in space and underwater applications. The fieldsequential colour display 404 is for accepting a field sequential coloursignal and for displaying said colour signal with little latency fromreceipt thereof. Timing diagram 420 shows the timing of sequentialcolour image fields produced by the field sequential colour camera 402,transmitted by the communication link 403 and displayed by the fieldsequential display 404. The sequential colour image fields areseparately sensed, transmitted and displayed. The display of informationrelating to a single sequential colour image field occurs before receiptof information relating to the next sequential colour image field. Inembodiment “A” 422 alternating fields cover the three primary colours insuccession for the odd image line numbers field, and then repeated forthe even image line numbers field. In embodiment “B” 424 the alternatingfields cover in succession the odd and even image line number fields forone primary colour and then the process is repeated for the other twoprimary colours. In embodiment “C” 426 both, the field—odd/even imageline numbers—and the primary colour at each new field, are alternated.The timing diagram 420 also shows a synchronization signal or flag 428at the beginning of the image field sequence. The synchronization signal428 ensures synchronization and sequence alignment of the alternatingfields. The field sequential colour camera 420 adds the synchronizationsignal 428 at the beginning of the image field sequence, which is thentransmitted to the field sequential colour display 404 forsynchronization and colour sequence alignment. Without thissynchronization signal 428, display technologies, even those using theinherent formatting of the incoming signal such as cathode ray tubes,have a possibility of sequence misalignment. For example a red cameraimage is displayed as a green display image. The synchronization signal428 also helps to avoid data buffering, which results in additional looplatency. One synchronization signal 428 is sufficient, as long as thefield sequential colour display 404 is for receiving a synchronizationsignal 428 at the relative position of this flag within the sequence.There are numerous other locations than the one shown in FIG. 4 forpositioning the synchronization signal 428 within the image fieldsequence. Table 430 shows the timing, frequencies and latency for thepresent invention—a custom built system. Timing and frequencies of priorart video systems are shown for comparison.

FIG. 5 shows embodiment “D” 522 of an anthropomorphic visualtelepresence system 500 according to the invention. A frame sequentialcolour camera 502 is linked by a communication link 503 to a framesequential display 504. The frame sequential colour camera 502 operateson the same basic principles as frame sequential colour camerasdescribed in prior art, excepting that an output therefrom is a framesequential colour signal. The communication link 503 is often a cablebut is sometimes a wireless communications. The field sequential colourdisplay 504 is for accepting a frame sequential colour signal and fordisplaying said colour signal with minimal latency from receipt thereof.Timing diagram 520 shows the timing of sequential colour image framesproduced by the frame sequential colour camera 502, transmitted by thecommunication link 503 and displayed by the frame sequential display504. The sequential colour image frames are separately sensed,transmitted and displayed. The display of information relating to asingle sequential colour image frame occurs before receipt ofinformation relating to the next sequential colour image frame. Table530 shows the timing, frequencies and latency for the present invention,Timing and frequencies of prior art video systems are shown forcomparison.

When the transmission time is negligible, the minimum latency in theembodiments “A”, “B”, “C” and “D” approaches zero (see tables 430 and530).

FIG. 6 shows embodiments “E”, “F” and “G” 600 corresponding toembodiments “A”, “B” and “C” of an anthropomorphic visual telepresencesystem according to the invention. The system comprises a fieldsequential colour camera 602, a communication link 603, digital imagecompression means 604 in the form of a digital image compressor, adigital data link 605, digital image decompression means 606 in the formof a digital image extractor for decompressing the compressed digitaldata, a communication link 607, and a field sequential colour display608. The field sequential colour camera 602 operates on the same basicprinciples as field sequential colour cameras described in prior art,excepting that an output therefrom is a field sequential colour signal.The digital image compressor 604 is preferably in the form of dedicatedhardware, firmware and software components implementing the compressionportion of a CODEC so as to efficiently compress the data received fromthe field sequential colour camera 602 via the communication link 603and thereby to maintain loop latency within reasonable limits. Thedigital data link 605 is often a cable but is sometimes a wirelesscommunications. The digital image extractor is for extracting datacompressed by the digital compressor, and is preferably in the form ofdedicated hardware, firmware and software implementing the decompressionportion of a CODEC so as to efficiently execute in reverse the algorithmused at the compression stage to restitute the original, uncompressedimage, sometimes with some level of resulting image degradation incomparison to its original counterpart. Timing diagram 620 shows atiming graph 622 of sequential colour image fields from the fieldsequential colour camera 602, a timing graph 624 of compressed digitaldata provided by the digital image compression means 604, and a timinggraph 626 of digital image data provided by the digital imagedecompression means 606 to the display 608. The timing diagram 620 alsoindicates a delay for compression 628 and decompression 629. The upperbound for the compression and decompression delay is preferably shorterthan the duration of a field 640. Table 630 shows the timing,frequencies and latency for the present invention with timing andfrequencies of prior art video systems for comparison.

FIG. 7 shows an embodiment “H” 700 corresponding to embodiment “D” ofthe anthropomorphic visual telepresence system according to theinvention. The system comprises a frame sequential colour camera 702, acommunication link 703, digital image compression means 704 in the formof a digital image compressor, a digital data link 705, digital imagedecompression means 706 in the form of a digital image extractor, acommunication link 707 and a frame sequential colour display 708. Theframe sequential colour camera 702 operates on the same basic principlesas frame sequential colour cameras described in prior art, exceptingthat an output therefrom is a frame sequential colour signal. Thedigital image compressor 704 is preferably in the form of dedicatedhardware, firmware and software components implementing the compressionportion of a CODEC so as to efficiently compress the data received fromthe frame sequential colour camera 702 via the communication link 703and thereby to maintain loop latency within reasonable limits. Thedigital data link 705 is often a cable but is sometimes a wirelesscommunications link. The digital image extractor is for extracting datacompressed by the digital compressor, and is preferably in the form ofdedicated hardware, firmware and software implementing the decompressionportion of a CODEC so as to efficiently execute in reverse the algorithmused at the compression stage to restitute the original, uncompressedimage, sometimes with some level of resulting image degradation incomparison to its original counterpart. Timing diagram 720 shows atiming graph 722 of sequential colour image fields from the fieldsequential colour camera 702, a timing graph 724 of compressed digitaldata provided by the digital image compression means 704, and a timinggraph 726 of digital image data provided by the digital imagedecompression means 706 to the display 708. The timing diagram 720 alsoindicates the delay for compression 728 and decompression 729. The upperbound for the compression and decompression delay is preferably shorterthan the duration of a single primary colour image or image portion wheninterlacing is used 740. Table 730 shows the timing, frequencies andlatency for the present and prior art video systems for comparison.

The use of anthropomorphic visual telepresence systems as described inFIGS. 6 and 7 is highly advantageous in applications where a remotecontrolled vehicle is exposed to high levels of radiation, for examplesolar wind and cosmic rays in space applications or radiation in nuclearfacilities, which hold the potential for at least indirectly distortinganalog signal transmission.

FIG. 8 shows another embodiment of an anthropomorphic visualtelepresence system 800 according to the invention. A field or framesequential colour camera 802 is linked by a communication link 803 to afield or frame sequential display 804. Connected to the camera 802 andthe display 804 are timing means 806 and 808 respectively. The timinginformation from the timing means 806 such as a Global PositioningSystem, GPS receiver, or other form of satellite-based globalpositioning system is embedded within a synchronization signal andtransmitted via the communication link 803. At the display 804, thistiming information is compared with timing information from timing means808 in order to determine loop latency. This is beneficial inapplications where the loop delay varies such as a highly mobilevehicle. For example, such a vehicle may require satellite communicationlinks for the digital data link when located in some areas. In otherareas, direct wireless communication is used. Because the digital datalink path length is significantly different between direct communicationlinks and those requiring satellites, such a timing marker isadvantageous. Furthermore, it enables implementation of time delaycorrection algorithms to alter the displayed image in order to alleviateadverse psycho-physiological effects of latency in visual telepresencesystems. Alternatively, a slow drift is used to vary timing from a firstlatency to a second latency when latency resulting from the digital datalink is substantially varied between image frames.

In an alternative embodiment, each image is encoded with further datacorresponding to sensor input. For example, vehicle speed is encodedinto each image in a same location and in a fashion that is intelligibleto an operator of the visual telepresence system. Encoding data in thisfashion is well known. For example, video cameras as are commonlyavailable often allow superposition of date or time information onto animage frame. Similarly, speed information could be superimposed ontoimages of a telepresence system.

Of course, numerous other embodiments may be envisaged without departingfrom the spirit and scope of the claimed invention.

1. An anthropomorphic visual telepresence system comprising: a) a headtracker for sensing movement of an operator's head; b) a sequentialcolour camera for capturing a colour image as a sequence of colourcomponent images; c) a servomechanism coupled to said camera andresponsive to signals from said head tracker to cause said camera totrack movements of the operator's head; d) said sequential colour cameragenerating a sequential output signal representing each of said capturedcomponent colour images in a sequence of time intervals; e) saidsequential colour camera inserting in each said sequence asynchronization signal to ensure synchronization and sequence alignmentof said component colour images captured by said sequential colourcamera; f) a head-mountable sequential colour display; and g) acommunications link for carrying said sequential output signal from saidsequential colour camera to said head-mountable sequential colourdisplay whereby said sequential output signal is applied as an input tosaid sequential colour display; h) said sequential colour display beingresponsive to said sequential output signal and said synchronizationsignal from said sequential colour camera to display said colour imageas said sequence of said colour component images.
 2. A sequential colourvisual telepresence system according to claim 1, wherein the sequentialcolour camera is a field sequential colour camera.
 3. A sequentialcolour visual telepresence system according to claim 2, wherein thesequential colour display is a field sequential colour display.
 4. Asequential colour visual telepresence system according to claim 1,wherein the sequence of captured colour component images comprises threesequential image portions covering the primary colours substantially forodd numbered image lines and three sequential image portions coveringthe primary colours substantially for even numbered image lines.
 5. Asequential colour visual telepresence system according to claim 1,wherein the sequence of colour component images comprises image portionssubstantially covering in succession odd numbered image lines and evennumbered image lines for one primary colour and then image portionssubstantially covering in succession odd numbered image lines and evennumbered image lines for another primary colour.
 6. A sequential colourvisual telepresence system according to claim 1, wherein the sequence ofcaptured images comprises image portions alternating between portionscomprising odd and even image lines, and wherein the primary colourchanges between captured images.
 7. A sequential colour visualtelepresence system according to claim 1, further comprising a digitalvideo transmitter for transmitting a digital video signal from thesequential colour camera to the sequential colour display over saidcommunications link.
 8. A sequential colour visual telepresence systemaccording to claim 1, further comprising: a) timing means connected tothe sequential colour camera for creating a timing signal; and, b)timing means connected to the sequential colour display, wherein thetiming signal is included in said sequential output signal.
 9. Asequential colour visual telepresence system according to claim 8,wherein the timing means comprises a GPS receiver.
 10. A sequentialcolour visual telepresence system according to claim 8, comprising atime delay correction algorithm.
 11. A sequential colour visualtelepresence system according to claim 1, wherein the sequential colourcamera is a frame sequential colour camera.
 12. A sequential colourvisual telepresence system according to claim 11, wherein the sequentialcolour display is a frame sequential colour display.
 13. A sequentialcolour visual telepresence system comprising: a) a head tracker forsensing movement of an operator's head; b) a sequential colour camerafor capturing a colour image as a sequence of colour component images;c) a servomechanism coupled to said camera and responsive to signalsfrom said head tracker to cause said camera to track movements of theoperator's head; d) said sequential colour camera generating asequential output signal representing each of said captured componentcolour images in a sequence of time intervals; e) said sequential colourcamera inserting in each said sequence a synchronization signal toensure synchronization and sequence alignment of said component colourimages captured by said sequential colour camera; f) a head-mountablesequential colour display; g) a communications link for carrying saidsequential output signal from said sequential colour camera to saidhead-mountable sequential colour display whereby said sequential outputsignal is applied as an input to said sequential colour display; h) saidsequential colour display being responsive to said sequential outputsignal and said synchronization signal from said sequential colourcamera to display said colour image as said sequence of said colourcomponent images; i) digital image compression means for sequentiallycompressing data representing the captured colour component imagesreceived from the sequential colour camera; and j) digital imagedecompression means for sequentially extracting the captured componentcolour images from the data compressed by the compression means, andwherein the communications link is a digital data link for transmittinginformation in the form of digital data.
 14. A sequential colour visualtelepresence system according to claim 13, wherein the digital imagecompression means comprises a digital image compressor.
 15. A sequentialcolour visual telepresence system according to claim 13, wherein thedigital image decompression means comprises a digital image extractor.